A trucker started a lethal chain of events early Tuesday morning when he stopped his semitrailer on U.S. 75, parking it in the middle northbound lane of the freeway. Its driver, Dwayne Simon, 37, didn't put his flashers on, police say; he just left the truck there in the dark at about 2:30 a.m.

Another driver traveling north on the freeway crashed his Chevy Silverado into the back of Simon's semi. The crash killed the Silverado's driver, whom police have not yet identified. Police closed U.S. 75 for about four hours to investigate the crash, causing major delays for drivers making their morning commutes.

TRAFFIC ALERT: All NB lanes of 75 are closed at 635, where police are investigating a fatal wreck. Traffic being diverted into service road. pic.twitter.com/OFvrFsB69q

Witnesses at the scene told police that Simon got out of the semi and began pacing around the truck, apparently incoherent. When Dallas Police Department officers showed up at the accident scene, Simon told them that he'd been driving north on U.S. 75 when he experienced mechanical problems that made it impossible to continue driving the truck. Police later found out that the truck was functional, they said Tuesday morning.

Police gave Simon a field sobriety test, which they say showed that Simon was under the influence of drugs at the time of the crash. DPD charged Simon with intoxication manslaughter and booked him into Dallas County Jail a little before 7 a.m. Tuesday. His bail hasn't been set.

Stephen Young has written about Dallas news for the Observer since 2014. He's a Dallas native and a graduate of the University of North Texas.